Merge pull request #755 from stan-dev/cleanup/no-32bit-makevar

Remove reference to outdated BITS=32 make variable

src/cmdstan-guide/installation.qmd

@@ -478,11 +478,6 @@ Execute the below commands to install the needed dependencies:
 pacman -Sy mingw-w64-ucrt-x86_64-make mingw-w64-ucrt-x86_64-gcc
 ```
 
-__32-bit Builds__
-
-CmdStan defaults to a 64-bit build. On a 32-bit operating system, you must specify
-the make variable `BIT=32` as part of the `make` command, described in the next section.
-
 [^1]:
 To open a Windows command shell, first open the __Start Menu__,
 (usually in the lower left of the screen), select option __All Programs__,
@@ -561,9 +556,9 @@ set the makefile variable `STAN_OPENCL` to `TRUE`:
 ```
 Makefile variables can also be set by creating a file named `local` in the
 CmdStan `make` subdirectory which contains a list of `<VARIABLE>=<VALUE>` pairs,
-one per line.   For example, if you are working on a 32-bit machine,
-you would put the line `BIT=32` into the file `<cmdstan-home>/make/local`
-so that all CmdStan programs and Stan models compile properly.
+one per line.   For example, to get the same effect as the above command
+every time, you would put the line `STAN_OPENCL=TRUE` into the file
+`<cmdstan_home>/make/local`.
 
 The complete set of Makefile variables can be found in file
 `<cmdstan-home>/cmdstan/stan/lib/stan_math/make/compiler_flags`.